Conventional hearing aids providing sound amplification do not provide any assistance to those persons classified as profoundly deaf. These persons have no measureable response to standardized hearing tests. Experimental tests have been conducted for profoundly deaf persons to implant an electrode into the cochlear region of the ear in the hope of electrically stimulating the nerves which transmits detected sounds to the brain.
It has been discovered that a conventional electrical audio signal, such as derived from a microphone, when applied to the implanted electrode, does not provide the stimulation for the subject corresponding to the sounds which generated the audio signal. It is therefore presumed that the ear must generate a neurological response which transmits the content of speech through the nerves of the ear to the brain in a manner distinctly different from the pure electrical analog of sound as transmitted through the air.
A number of experimentors have studied coding patterns for transforming an electrical audio signal into a driver signal for an auditory implant. To date, these tests have had only minimal success. Although subjects have been able to perceive the existence of the simulated sounds, the actual recognition and discrimination of words has been poor.
In view of the possibility of providing some degree of hearing ability to the profoundly deaf by means of auditory implants, there exists a need for a method and apparatus for encoding and processing speech signals in real time to provide a driver signal for an implant such that the subject is able to perceive and distinguish speech.